ויהי השמש באה AND IT CAME TO PASS, WHEN THE SUN WENT DOWN —Similar syntactical constructions are (42:35) ויהי הם מריקים שקיהם “And it came to pass when they were emptying their sacks”, and (2 Kings 13:21) ויהי הם קוברים איש “and it came to pass when they were burying a man” — as much as to say, and this thing happened (i. e. after ויהי supply the words דבר זה: “And this thing happened: the sun set etc.”)

באה IT (SHE) CAME — The accent is on the first syllable, consequently it must signify that it (the sun) had already set. If, however, the accent were on the last syllable, on the א, it would signify that there was darkness whilst it was setting (i. e. the former is a perfect, the latter a participle). It is impossible to explain it thus here (that it means the sun was setting) because it has already been stated (v. 12) “And it came to pass that when the sun was setting”, and the passing of the smoking furnace took place after this — consequently the sun had set already when it passed. This is the difference in the case of every word (verb), feminine gender, whose root has two letters, as בא ,קם ,שב: when the accent is on the first syllable, it is the perfect tense, as is this word באה here, and like (19:9) “And Rachel (באה) came”; (37:7) “And my sheaf קמה arose”; (Ruth 1:15) “Behold, thy sister-in-law (שבה) has gone back”; but when the accent is on the last syllable it is a present tense (participle), denoting an action being done now and continuing to be done, as for instance, (29:6) “She is coming (באה) with the sheep”; (Ester 2:14) “In the evening she used to come (באה) and in the morning (שבה) she used to return”.